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Dart/Flutter now has macros/metaprogramming

github.com

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Re: Dart/Flutter now has macros/metaprogramming

#4

Post by millsteed »

mikenew wrote: post #2

This is the actual spec: https://github.com/dart-lang/language/blob/main/working/macr... Not really sure what the linked repo is about.

Thanks for linking the spec. It has been a living document for a long time. I discovered that the implementation had made it into the SDK's master branch. Since it's very early stage and lacking documentation, I made this repo which demonstrates creating a macro that implements some of the most popular codegen functionality Flutter developers use.

Re: Dart/Flutter now has macros/metaprogramming

#7

Post by cogman10 »

ivanjermakov wrote: post #6

Looks very similar to the Reflection API in Java.

It's more akin to Java's annotation processor. It's generating code at compile time and not runtime.

Dart has runtime reflection and annotations that predate this. The benefit of making this compile time are mainly performance.

Re: Dart/Flutter now has macros/metaprogramming

#8

Post by millsteed »

ivanjermakov wrote: post #6

Looks very similar to the Reflection API in Java.

Yeah, it is. It inspired the reflection in Dart, which inspired the macros. You can only use Dart's reflection when running in VM mode though. Flutter apps use AOT compilation, due to tree-shaking, so you lose the reflection and fall back to having to run codegen - kind of like TypeScript -> JS. This is a nice improvement that is run in memory before compilation and allows better access to the AST.

Re: Dart/Flutter now has macros/metaprogramming

#9

Post by millsteed »

cogman10 wrote: post #7
ivanjermakov wrote: post #6

Looks very similar to the Reflection API in Java.

It's more akin to Java's annotation processor. It's generating code at compile time and not runtime. Dart has runtime reflection and annotations that predate this. The benefit of making this compile time are mainly performance.

Don't discount the developer experience too. With the codegen annotations, you either have to check in your .g.dart files to git which could be stale and break compilation in CI, or have them generate in CI, which is unnecessarily slow and eats up CI minutes. Added bonus is the macro API is less complex than the codegen API.
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